494 
BRITISH ASSOCIATION MEETING. 
(Professor Owen's 4ddress.— Ccmtinued from page 450.) 
Last year, M. Poitevin's production of plates of relief for the pui-pose of 
engraving by the action of light alone was cited as the latest marvel of photo- 
graphy. This year has witnessed photographic printing in carbon by M. Pretschi. 
M. Niepce de St. Victor has succeeded in reproducing the colour of the original 
on metallic plates, though be cannot fix it; and these lovely " heliochromes " 
unfortunately vanish like the breath from a mirror. Mr. Scaife has obtained a 
portrait of a shell in full flight a few feet after it left the mortar, with a repre- 
sentation of phenomena in the development of the smoke too transitory for the 
eye to ascertain when they occur. Photography may hence superadd a new 
defining function to the highest attainable telescopic power. 
The first application of the electro-magnetic discovery was, as it nhould be, 
to the direct service of the philosopher. The application of a delicate compass- 
needle would show by its delicate deflection the strength of the voltaic current. 
Out of this followed the knowledge of thermo-electricity. Faraday's demonstra- 
tion — the converse of Oersted's — that magnetism could produce electricity, has 
been succeeded by other brilliant discoveries by that most exemplary investigator 
of natural laws. Out of Oersted's painfully-pursued experiments with his little 
magnets, voltaic pile, and bits of copper-wire has come tlie electric telegraph ! 
Bacon, commenting on the " History of the works of Nature," describes it as a 
chaos of " fables, antiquities, quotations, frivolous disputes, philology, ornaments, 
and table-talk." Since his day, the chief steps by which natural history has 
advanced to the dignity of a science are associated with the names of Ray, 
Linnseus, Jussieu, Buifon, and Cuvier. Now, not only has the structure of the 
animal been investigated even to the minute characteristics of each tissue, but 
the mode of formation of such constituents of organs, and of the organs themselves, 
lias been pursued from the germ, bud, or egg, onward to maturity and decay. 'J o 
the observation of outward characters is now added that of inward organization 
and developmental change, and zootomy, histology, and embryology combine their 
results in forming an adequate and lasting basis for the higher axioms and 
gent raliz.itions of zoology properly so-called. 
The study of homologous parts in a single system of organs — the bones — has 
Eaainly led to the recognition of the plan or archetype of the highest primary 
group of animals, the vertebrata. The next step of importance will be to deter- 
mine the homologous parts of the nervous system, of the muscular system, of the 
respiratory and vascular systems, and of the digestive, secretory, and generative 
organs in the same primary group or province. It is of more importance to settle 
the homologous of the parts of a group of animals than to speculate on such rela- 
tions of parts in animals constructed on demonstratively distinct plans of organi- 
zation. What has been efiected and recommended in regard to homologous parts 
in the Vertebrata should be followed out in the Articulata and Molliisca : — 
" The present state of homology in regard to the Artieidata has suflBced to 
demonstrate that the segment of the crust is not a hollow expanded homologue of 
the segment of the endoskeleton of a vertebrate. There is as little homology 
between the parts and appendages of the segments of the vertebrate and articu- 
late skeletons respectively. The parts called mandibles, maxillae, arms, legs, 
■wings, fins, in insects and crustaceans, are only 'analogous' to the parts so called 
in Vertebrates ; and to express definitely the clear ideas now possessed of their 
essential distinction, will require a distinct nomenclature." 
The investigations of the vitellus, of the entozoa, of the metamorphoses of insects, 
and the subjects investigated by means of the microscope, are next passed under 
review. 
A very interesting application of the microscope to the examination of the par- 
ticles of matter suspended in the atnio.sphere has been made. Cloudy extents of 
dust-like matter pervading the atmosphere, which have been variously observed. 
Lave been thus found to consist of the pollen of plants, vegetable species, and 
L)iutomaceae, and this investigation promises to be productive of otlier important 
results. 
